U.S. patent application number 13/859383 was filed with the patent office on 2013-08-29 for system and method for forming of tubular parts.
This patent application is currently assigned to NEW JERSEY INSTITUTE OF TECHNOLOGY. The applicant listed for this patent is NEW JERSEY INSTITUTE OF TECHNOLOGY. Invention is credited to Ernest Samuel Geskin, Krzysztof Kluz.
Application Number | 20130220473 13/859383 |
Document ID | / |
Family ID | 43878378 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220473 |
Kind Code |
A1 |
Geskin; Ernest Samuel ; et
al. |
August 29, 2013 |
SYSTEM AND METHOD FOR FORMING OF TUBULAR PARTS
Abstract
Apparatus and methods are disclosed whereby a propellant driven
water stream is used in the formation of materials made from high
tensile strength alloys. High pressure developed in liquid flowing
through a tubular work piece is employed to achieve desired forms.
The high pressure results from superposition of compression waves
generated in the course of the impact of the liquid by products of
propellant combustion.
Inventors: |
Geskin; Ernest Samuel;
(Florham Park, NJ) ; Kluz; Krzysztof; (Saddle
Brook, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEW JERSEY INSTITUTE OF TECHNOLOGY; |
|
|
US |
|
|
Assignee: |
NEW JERSEY INSTITUTE OF
TECHNOLOGY
Newark
NJ
|
Family ID: |
43878378 |
Appl. No.: |
13/859383 |
Filed: |
April 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12905556 |
Oct 15, 2010 |
8459078 |
|
|
13859383 |
|
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61251997 |
Oct 15, 2009 |
|
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61298662 |
Jan 27, 2010 |
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Current U.S.
Class: |
138/155 ;
72/56 |
Current CPC
Class: |
F16L 9/22 20130101; B21D
26/08 20130101; Y10S 72/706 20130101; Y10T 29/49806 20150115 |
Class at
Publication: |
138/155 ;
72/56 |
International
Class: |
F16L 9/22 20060101
F16L009/22; B21D 26/08 20060101 B21D026/08 |
Claims
1. A method of forming a workpiece into a desired shape comprising
providing a die having an interior cavity configured to receive a
workpiece, wherein the interior cavity comprises a dimension and
shape corresponding to a desired shape of a finished workpiece,
providing a combustion chamber adjacent one end of the die and a
tapered nozzle adjacent an opposite end of the die, providing the
nozzle with a relief opening at an end thereof, positioning the
combustion chamber, die and nozzle in axially alignment, inserting
a workpiece having two opposing open ends in the die cavity in
axial alignment with the combustion chamber, die and nozzle,
loading a propellant charge in the combustion chamber, filling the
workpiece with a liquid, and activating the propellant charge.
2. The method according to claim 1 further comprising positioning
an ignition mechanism adjacent to the combustion chamber and using
the ignition mechanism to initiate a combustion event.
3. The method according to claim 1 further comprising providing a
fluid supply to the workpiece.
4. The method according to claim 1 wherein the workpiece is
tubular.
5. The method according to claim 1 comprising generating forming
pressure of at least 1 GPa.
6. A tubular device comprising a section having a tube diameter
greater than a diameter of an adjacent section, the section having
a tube diameter greater than a diameter of an adjacent section
formed by a process comprising providing a die having an interior
cavity configured to receive a tubular workpiece, providing the die
with an interior cavity having a dimension and shape corresponding
to a desired shape of a the tubular device to be formed from the
workpiece, providing a combustion chamber adjacent one end of the
die and a tapered nozzle adjacent an opposite end of the die,
providing the nozzle with a relief opening at an end thereof,
positioning the combustion chamber, die and nozzle in axially
alignment, inserting the workpiece having two opposing open ends in
the die cavity in axial alignment with the combustion chamber, die
and nozzle, loading a propellant charge in the combustion chamber,
filling the workpiece with a liquid, and activating the propellant
charge.
7. The device made according to claim 6 further comprising
positioning an ignition mechanism adjacent to the combustion
chamber and using the ignition mechanism to initiate a combustion
event.
8. The device made according to claim 6 further comprising
providing a continuous fluid supply to the apparatus.
9. The device made according to claim 6 comprising generating
forming pressure reaching and/or exceeding 1 GPa.
10. The device made according to claim 6 wherein the device is a
bleed tube for the compressor high pressure stage.
11. The device according to claim 6, the section having a tube
diameter greater than a diameter of an adjacent section comprising
a tube diameter from 12.29 to 55% greater than a diameter of the
adjacent section.
12. The device according to claim 6, the section having a tube
diameter greater than a diameter of an adjacent section comprising
a cross sectional area 4.6% to 16.2% greater than a cross sectional
area of the adjacent section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/905,556 filed Oct. 15, 2010 which claims
the benefit of U.S. Provisional Patent Application No. 61/251,997
filed Oct. 15, 2009 and U.S. Provisional Patent Application No.
61/298,662 filed Jan. 27, 2010, the entireties of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the use of a liquid, such
as water, as a medium for conversion of available chemical,
mechanical or electrical energy into kinetic energy. In particular
the present invention relates to apparatus for, and methods of,
forming materials of high tensile strength such as alloys using
propellant driven water streams.
BACKGROUND OF THE INVENTION
[0003] Almost any mechanical device contains hollow shapes, such as
tubes, shafts, shells, housings and the like. Such features as the
ability to contain and guide liquid streams, minimal
weight-to-strength ratio, etc. make these parts indispensable in
the design of practically any mechanical device or system. It has
long been a goal of manufacturers to improve geometry, precision,
and mechanical properties of hollow parts since to do so would
enhance energy efficiency and reliability of a number of devices.
Such improvements would be especially valuable and important for
the aerospace industry where weight minimization is one of the key
objectives of aircraft design. However, in many cases the geometry
and material choice of hollow parts are determined by the cost of
fabrication rather than design optimization. Currently, deformation
of hollow objects is commonly carried out by the use of
hydroforming and explosive forming. Despite several obvious
advantages, these processes have their shortcomings.
[0004] Hydroforming is a quasi-static process that changes the
shape of a hollow part without significant expansion of the part.
The drawbacks of the hydroforming process include unpredictable
wall thinning in die corners, insufficient dimensional
repeatability, lack of concentricity, and work hardening. These
features impede process applications for forming repeatable,
precise, and structurally sound expanded components. Moreover, to
obtain expansions in the range of 20%, an axial tube feed is
required. Another significant obstacle preventing wide adoption of
a hydrostatic expansion technique is the high capital cost of
forming equipment (pumps, presses, etc.).
[0005] Explosive forming is a high energy rate process that became
established in the metal forming industry in the 1960s and 1970s.
The method has been especially useful in the aerospace, gas
turbine, and nuclear industries. The need for large components,
produced in small runs and within short lead times, has been the
driving force behind the development of this method. The main
disadvantage of explosive forming is the lack of ability to produce
small, precise, or large manufacturing volume parts. Moreover, the
technology must be handled by well trained personnel and in remote
facilities.
[0006] Thus there is a need in the art for systems and processes
which overcome the deficiencies of traditional hydroforming and
explosive forming techniques.
SUMMARY OF THE INVENTION
[0007] One aspect of the present invention relates generally to
apparatus and processes whereby a propellant driven water stream is
used in the formation of materials made from high tensile strength
alloys. In accordance with the present disclosures high pressure
developed in liquid flowing through a tubular work piece is
employed to achieve desired forms. This high pressure results from
superposition of compression waves generated in the course of the
impact of the liquid by products of propellant combustion.
[0008] In one embodiment, a system for forming a tubular component
into a desired shape is provided, which system includes a die
assembly and a combustion chamber for generating gas, whereby water
is driven through a workpiece located in the die assembly to mold
the tubular workpiece in the form provided by the die. The
combustion chamber may include a propellant charge, such as a
cartridge containing propellant. An ignition mechanism may be
included to initate combustion.
[0009] In another embodiment, a method of forming a tubular
component into a desired shape is provided which includes using a
die assembly to receive a tubular component, using a combustion
chamber to generate a gas, supplying a flow of liquid through the
workpiece and driving water through a tubular workpiece using the
gas generated by the combustion chamber, whereby the water impacts
the tubular workpiece with force sufficient to mold the tubular
workpiece in the form provided by the die.
[0010] In one embodiment an apparatus is provided for forming a
workpiece into a desired shape comprising a die having an interior
cavity configured to receive a workpiece, the die interior cavity
having a dimension and shape corresponding to a desired shape of a
finished workpiece, a combustion chamber adjacent one end of the
die and a tapered nozzle adjacent an opposite end of the die, the
nozzle having a relief opening at an end thereof, the combustion
chamber, die and nozzle being axially aligned. The die is
configured to receive a workpiece having two open ends, the open
ends being receiveable so that they are aligned axially with the
combustion chamber and the nozzle, such that the first open end of
the workpiece is adjacent the combustion chamber and the second
open end is adjacent the nozzle.
[0011] The apparatus may include an ignition mechanism positioned
adjacent to the combustion chamber and operable to initiate a
combustion event in the combustion chamber. The combustion chamber
is configured to receive a propellant charge oriented so that upon
an initiating event, the propellant material is expelled along the
axial direction of the workpiece.
[0012] In another embodiment the die is a split die.
[0013] In one embodiment the apparatus includes an inlet to feed
liquid to an interior space of a tubular workpiece. A fluid supply
may be included to provide fluid flow continuously through a
tubular workpiece.
[0014] In accordance with another embodiment a method of forming a
workpiece into a desired shape is provided which includes providing
a die having an interior cavity configured to receive a workpiece,
providing the die with an interior cavity having a dimension and
shape corresponding to a desired shape of a finished workpiece,
providing a combustion chamber adjacent one end of the die and a
tapered nozzle adjacent an opposite end of the die, providing the
nozzle with a relief opening at an end thereof, positioning the
combustion chamber, die and nozzle in axially alignment, inserting
a workpiece having two opposing open ends in the die cavity in
axial alignment with the combustion chamber, die and nozzle,
loading a propellant charge in the combustion chamber, filling the
workpiece with a liquid, and activating the propellant charge. The
method may include positioning an ignition mechanism adjacent to
the combustion chamber and using the ignition mechanism to initiate
a combustion event. The method may include providing a continuous
fluid supply to flow through the tubular workpiece. In another
embodiment the foregoing processes may include generating forming
pressure reaching and/or exceeding 1 GPa.
[0015] In another embodiment, a method of forming a tubular
workpiece into a desired shape is provided which includes providing
a combustion chamber adjacent a first open end of a workpiece to be
shaped, positioning a nozzle adjacent a second, opposite open end
of the tubular workpiece, filling the workpiece with a liquid,
positioning a die around the workpiece, activating a propellant
charge in the combustion chamber and using resulting combustion and
the water to transfer accumulated energy to the workpiece through
compression waves.
[0016] In another embodiment a tubular device is provided made by a
process comprising providing a die having an interior cavity
configured to receive a tubular workpiece, providing the die with
an interior cavity having a dimension and shape corresponding to a
desired shape of a the tubular device to be formed from the
workpiece, providing a combustion chamber adjacent one end of the
die and a tapered nozzle adjacent an opposite end of the die,
providing the nozzle with a relief opening at an end thereof,
positioning the combustion chamber, die and nozzle in axially
alignment, inserting the workpiece having two opposing open ends in
the die cavity in axial alignment with the combustion chamber, die
and nozzle, loading a propellant charge in the combustion chamber,
filling the workpiece with a liquid, and activating the propellant
charge.
[0017] In another embodiment the device made according to the
foregoing process includes generating forming pressure reaching
and/or exceeding 1 GPa. In yet a further embodiment the device made
according to the foregoing process is a bleed tube for the axial
compressor high pressure stage.
[0018] Exemplary embodiments in accordance with the present
disclosure show that the forming of hollow parts can be achieved
effectively if high energy rate deformation is carried on in an
open system rather than in a sealed container. Using certain
exemplary applications of the disclosures herein it has been shown
that despite large strains, exceeding in some cases the static test
elongation limit, samples generated in accordance with the present
disclosures were characterized by a uniform wall thinning and
structural integrity. For example, a 55% expansion of Ti-3A1-2.5V
tube was attained using a simple setup employing an embodiment
disclosed herein. Acquired experimental data show that the
presently disclosed apparatus and methods can be applied to form
alloys characterized by high tensile strength, low static
elongation limits, and low modulus of elasticity. The dimensional
stability, feasibility of large deformations, safety of use,
ability to form small precise parts in large quantities, and
compact and inexpensive facilities are some of the advantages of
the present disclosures in comparison to conventional quasi-static
hydro expansion, hot forming, and high energy rate explosive
forming techniques.
[0019] Given above is a simplified summary of the disclosure in
order to provide a basic understanding of some aspects described
herein. The advantages described herein and others will be apparent
to those having skill in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] To assist those of ordinary skill in the relevant art in
making and using the subject matter hereof, reference is made to
the appended drawings, wherein:
[0021] FIG. 1 depicts an apparatus for forming a workpiece in
accordance with an aspect of the present disclosure;
[0022] FIG. 1A depicts an ignition apparatus in accordance with an
aspect of the present disclosure;
[0023] FIGS. 1B and 1C depict an embodiment for continuous water
delivery to an apparatus subject to interruption by a check valve
in accordance with an aspect of the present disclosure;
[0024] FIGS. 2 and 2A are pictorial (FIG. 2) and graphical (FIG.
2A) depictions numerically obtained, time dependent pressure at
different points of a rigid tube (barrel) in accordance with an
aspect of the present disclosure;
[0025] FIG. 3 presents photographs of a sample of AMS 5557 tube
material having one side expanded formed in accordance with an
aspect of the present disclosure;
[0026] FIG. 4 presents dimensional analyses of the sample in
accordance with FIG. 3;
[0027] FIG. 5 presents dimensional analyses of a sample of AMS 4943
tube material formed in accordance with an aspect of the present
disclosure;
[0028] FIG. 6 presents photographs of a sample of AMS 5581 tube
material having two sides expanded formed in accordance with an
aspect of the present disclosure;
[0029] FIG. 7 dimensional analyses of the sample in accordance with
FIG. 6;
[0030] FIG. 8 presents dimensional analyses of a sample of AMS 4943
tube material formed in accordance with an aspect of the present
disclosure;
[0031] FIG. 9 presents photographs of metallographic samples of AMS
4943 tube material showing two-sided deformation in accordance with
an aspect of the present disclosure;
[0032] FIG. 10 presents a photographic side view of a sample of AMS
4943 tube material formed in accordance with an aspect of the
present disclosure, showing 55% symmetric expansion, wherein the
original tube wall thickness=0.0355 in. (0.90 mm);
[0033] FIG. 10A is a cross-sectional view of the sample in
accordance with FIG. 10 indicating symmetric expansion of a portion
thereof;
[0034] FIG. 11 presents photographs of a sample of AMS 5881 heat
shield tube material with multiple elliptical cross-sections formed
in accordance with an aspect of the present disclosure;
[0035] FIG. 12 is a photographic top plan view of a workpiece
formed into a compressor high pressure stage bleed tube in
accordance with an aspect of the present disclosures; and
[0036] FIG. 12A is a photographic side view of a detail of the
compressor high pressure stage bleed tube of FIG. 12.
[0037] It should be noted that the appended drawings illustrate
only typical embodiments of this invention and are therefore not to
be construed as limiting of its scope, for the invention may admit
to other equally effective embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0038] The following is a detailed description of the invention
provided to aid those skilled in the art in practicing the present
invention. Those of ordinary skill in the art may make
modifications and variations in the embodiments described herein
without departing from the spirit or scope of the present
invention. Unless otherwise defined, all technical and scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which this invention belongs.
The terminology used in the description of the invention herein is
for describing particular embodiments only and is not intended to
be limiting of the invention. All publications, patent
applications, patents, figures and other references mentioned
herein are expressly incorporated by reference in their
entirety.
[0039] In the following description, for purposes of explanation,
specific numbers, materials and configurations are set forth in
order to provide a thorough understanding of the invention. It will
be apparent, however, to one having ordinary skill in the art that
the invention may be practiced without these specific details. In
some instances, well-known features may be omitted or simplified so
as not to obscure the present invention. Furthermore, reference in
the specification to phrases such as "one embodiment" or "an
embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. The
appearances of phrases such as "in one embodiment" in various
places in the specification are not necessarily all referring to
the same embodiment.
[0040] In general, the presently disclosed apparatus and methods
employ a deformation force developed by superposition of
compression waves generated in an impact accelerated stream flowing
through a tubular work piece confined by a die. Superposition of
compression waves, developing in a moving fluid, brings about
formation of pressure pulses, which by far exceed the impact
pressure at the free surface boundary of the liquid. The result is
a tubular workpiece conformed to the shape and dimension of the
interior cavity of the die.
[0041] In one aspect of the present invention, the products of
propellant combustion are used to impact a liquid filling a tubular
work piece and expel the liquid via a nozzle. Now referring to FIG.
1, an apparatus 10 for forming a workpiece in accordance with the
present disclosures includes a die assembly 2, a combustion chamber
20, and an ignition mechanism 30. The die assembly 2 has an
interior cavity 3 having a dimension and shape corresponding to the
desired final form of a workpiece 40. The apparatus 10 includes a
combustion chamber 20 adjacent one end of the die and a nozzle 8
adjacent the opposite end of the die 2, the nozzle having a relief
opening 9 at the nozzle tip. The die 2 is configured to receive the
workpiece 40 such that one end 42 of the workpiece 40 is adjacent
the combustion chamber 20 and the other end 44 is adjacent the
nozzle 8.
[0042] The ignition mechanism 30 is positioned adjacent the die 2
and combustion chamber 20 for initiation of combustion.
[0043] The combustion chamber 20 may in one embodiment be operable
to receive a propellant charge 22 such as a propellant cartridge
containing propellant material 24. Propellant charge 22 may be a
commercially available cartridge such as, Remington 38 Special
Blank 38BLNK, Winchester 38SBLP, 38 Special Blank, and CCI .22
Smokeless Short Noise Blank, .22 Caliber. It will be apparent to
those skilled in the art any suitable cartridge may be used, such
that a desired propellant type and amounts may be used for a
particular application. Propellant material 24 may be a
nitrocellulose-based fast burning propellant material such as
Winchester.RTM. WC760 smokeless powder, Winchester.RTM. 231,
IMR.RTM. 3031, and IMR.RTM. 7828. The propellant to water weight
ratio depends on the extent of deformation to be performed, tube
size, and mechanical properties of tube material. In experiments
performed the effective weight ratio ranged between 1/10 and 1/20.
The propellant charge 22 is fitted in the combustion chamber 20 so
that the workpiece end 42 adjacent to the ignition mechanism 30 is
in tight connection therewith so that the propellant material 24 is
expelled along the axial direction of the workpiece 40.
[0044] Now referring to FIG. 1A, an embodiment of an ignition
mechanism 30 is disclosed which may be used to initiate the process
of propellant combustion. Ignition mechanism 30 may include a
support 31, impact pin 32, primer pin 33, initiation spring 34 and
safety pin 35. Support 31 may engage die 2 using any suitable
securing means including but not limited to a threaded engagement
as shown, bolting, clamping, latching, or the like. In the depicted
embodiment the support 31 maintains the position of the impact and
primer pins 32 and 33, respectively, and prevents recoil. The
support 31 also prevents the escape of combustion products. The
safety pin 35 may be removed to actuate the ignition mechanism.
[0045] In one embodiment the die 2 is made of two halves, which
when fitted together provide a desired interior cavity dimension
and shape to which the finished workpiece 40 conforms. Such a split
die permits simple disassembly and work piece removal. The dies may
be made of any suitable material, such as general purpose low
carbon steel, such as low carbon steel 1018. In certain exemplary
embodiments, the cavities are cast with CerroBend 158, a low
temperature melting alloy with tensile strength of 41 MPa, 9.2
Brinell hardness, and melting temperature of 70.degree. C.
[0046] In preparation for use of the apparatus 10, a fluid 50 is
introduced into the workpiece 40. Fluid 50 may be any suitable
liquid such as water. Liquid 50 may be introduced for example
through the combustion chamber 20 prior to insertion of the
propellant charge 22. The nozzle 9 may be plugged by any suitable
means, such as but not limited to paraffin, to prevent escapement
of liquid 50. Now referring to FIGS. 1B and 1C, in one embodiment
an inlet 60 is provided in the apparatus 10 to feed liquid 50 to an
interior space of a workpiece 40. For commercial high volume
applications, the apparatus 10 may include an inlet 60 to supply
fluid 50 continuously to the apparatus 10 for introduction to the
workpiece 40. In one embodiment, a check valve 62 and spring are
positioned between the combustion chamber 20 and the workpiece 40
in proximity to the inlet 60. A water compression chamber 66 may be
provided between check valve 62 and workpiece 40. The check valve
62 is shown in FIG. 1B in an upper position, before ignition, such
that the inlet 60 is open. In FIG. 1C the check valve 62 is shown
in the closed position, upon combustion, which stops the flow of
liquid 50 to the interior space of the workpiece 40. The check
valve 62 acts as a piston to transfer impact energy into the liquid
50 and generate pressure waves. Upon completion of the combustion
event, the spring 64 restores the check valve 62 to the open
position, permitting water to enter the workpiece 40.
[0047] In a method in accordance with one embodiment, a workpiece
40 is inserted in die 2. Prior to the activation of the ignition
mechanism 30, the workpiece 40 is filled with a liquid 50 such as
water. A propellant charge is loaded into apparatus 10. The
propellant charge is activated. The water 50 works as a powerful
forming medium. It accumulates energy generated in the course of
propellant combustion and subsequently transfers it to the work
piece 40 through propagated, refracted, and reflected compression
waves. Pressure amplification results from the superposition of
compression waves. Consequently, the workpiece 40 absorbs the
energy of the compression wave and deforms adopting the shape of
the die cavity 3. Due to the high rate of the energy release (the
duration of combustion is typically less than 0.5 ms), embodiments
of the present disclosures can be classified as high-energy rate
forming processes wherein a tubular object, confined by a die, can
be successfully processed to form a desired shape.
[0048] Now referring to FIGS. 2 and 2A, the calculated values
represent the numerically obtained, time dependent pressure at
different points of a rigid tube (barrel) in experimentation on one
particular exemplary embodiment. The geometry of said embodiment
corresponds to the dimensions of tubular components tested. For
this exemplary embodiment, the graph shows clearly that the incited
compression wave is most intense near the nozzle entrance. Other
points, closer to the combustion chamber of said exemplary
embodiment, are characterized by lower amplitudes, the values of
which decrease in the course of time and with increasing distance
from the nozzle. The pressure functions at points p2, p3, p4 for
said embodiment have the same phase, which is opposite to the
pressure function at point p1. The pressure at point p1 relates to
the impact pressure created by rapid combustion of the cartridge
propellant, while the pressures at points p2, p3, p4 are the
responses to the applied impact for said embodiment. Due to the
oscillatory mode of the pressure variation, caused by traveling
waves, the process in question has been defined as a compression
pulse forming. The presently disclosed forming technique, utilizing
induced compression pulses, differs from explosive forming and
hydro expansion processes in that the apparatus employed uses
non-constrained component ends, employs low explosive with
incompressible fluid, eliminates axial feed, requires no sealing,
and uses a converging nozzle as a flow control.
[0049] Depending on the internal work piece geometry, the pressure
at the nozzle entrance can exceed the pressure of combustion
products by a factor of two for certain exemplary embodiments.
Thus, the impact pressure generated in the combustion chamber can
be significantly lower than the forming pressure for these
exemplary embodiments. Hoop stresses, resulting from high pressure
exerted on a workpiece, cause its plastic deformation. A tube or
another work piece absorbs these stresses and protects the die
assembly. Therefore, it is possible to generate pressure in the
order of several GPa needed for processing of thick walled
components in accordance with the present disclosures.
[0050] The magnitude of pressure exerted on a work piece can be
precisely controlled by component geometry, propellant mass, and
its properties. Existing pumps cannot generate comparable pressure
nor maintain its oscillatory mode, which contributes toward axial
material flow.
[0051] The compression pulse methods described herein and utilized
in the experiments and examples herein are effective in forming of
high tensile strength tubing. The simplicity of design and
operation and low capital cost make this method suitable for both
rapid prototyping and high volume manufacturing. The technology
enables generation of metal components, which could either not be
made at all or could only be made at very high cost using existing
technologies. The disclosed processes can eliminate the need for
welded joints, which otherwise would be required to assemble a
desired shape in the middle of the tube section. Further, formed
shapes can replace certain machined components and reduce the
weight of an assembly.
[0052] Water pressure generated in accordance with the present
disclosures exceed the ultimate yield stress of materials such as
metals and high strength alloys, such as, for example, those
currently used in the aerospace industry. Alloys such as stainless
steel 321, Inconel 625, and Ti-3A1-2.5V are of particular interest
since they represent the main tube materials used in aerospace
engines. These alloys are used only to illustrate potential
commercial applications in the aerospace industry. The skilled
artisan will recognize the present disclosures contemplate wider
application to many industries using a wide range of metals and/or
alloys. Because of the extremely short duration of forming in
accordance with the present disclosures, there is no need for
special provisions to seal a die assembly or work piece. The
duration of the forming process is less than the time needed for
draining the internal space of a work piece and die assembly.
Experiments
[0053] Testing of three alloys extensively used in aerospace and
gas turbine industries provided experimental data about embodiments
of this novel forming technology. The alloys, assigned with
aerospace specifications, were AMS 5557, AMS 5581, and AMS 4943.
Common commercial names for them are stainless steel 321, Inconel
625, and Ti-3A1-2.5V (ASTM Grade 9), respectively. The AMS
(Aerospace Material Specification) designation is not only
pertinent to chemical and mechanical properties, but also specifies
the form of the material used. The materials were provided in the
form of seamless tubing. They were annealed, stress relieved, and
hydrostatically tested. Table 1 provides chemical composition of
the tested alloys while Table 2 presents the mechanical properties
thereof
TABLE-US-00001 TABLE 1 Alloy Type Chemical Composition in % AMS C =
0.046 Mn = 1.64 P = 0.025 S = 0.001 5557 Cr = 17.5 Ni = 10.65 Mo =
0.38 Cu = 0.24 Si = 0.44 Ti = 0.32 N = 0.014 Fe = Bal AMS C = 0.02
Mn = 0.29 P = 0.008 S < 0.002 Si = 0.16 5581 Cbta = 3.44 Co =
0.29 Ti = 0.26 Al = 0.25 Fe = 4.14 Cr = 21.69 Ni = 60.0 Mo = 8.71
Cb = 3.39 Ta < 0.05 AMS AL = 3.06 B < 0.0005 C = 0.005 Cu
< 4943 0.0025 O = 0.0940 Si = 0.012 Ti = Bal V = 2.47 Fe = 0.128
W < 0.003 Y < 0.0005
TABLE-US-00002 TABLE 2 0.2% Offset Tensile Yield Yield Alloy Type
Strength Strength Strength Elongation AMS 5557 638 MPa 286 MPa --
42% AMS 5581 958 MPa -- 541 MPa 47% AMS 4943 636 MPa -- 560 MPa
26%
[0054] The forming system of one particular embodiment of the
present invention, illustrated in FIG. 1, is one of the simplest
systems for practical application of the disclosed methods. A
forming tool in accordance with FIG. 1 was designed, engineered,
and manufactured in the Water Jet Laboratory at NJIT. For purposes
of the experiments, the die was made of two halves, which
reproduced the final product shape. The die was designed to allow
simple disassembly and work piece removal. For said embodiment, the
dies were made of general purpose, low carbon steel 1018, which
performed adequately. In certain experiments, the cavities were
cast with CerroBend 158, low temperature melting alloy with tensile
strength of 41 MPa, 9.2 Brinell hardness, and melting temperature
of 70.degree. C. No provisions for air removal from the die
cavities were made in these particular exemplary embodiments.
[0055] One experiment involved expansion of the AMS 5557 alloy. The
sample was represented by a standard aerospace schedule seamless
tube with a diameter of 12.70 mm, wall thickness of 0.89 mm, and
length of 118.62 mm. The die cavity and consequent expansion were
not symmetrical in regard to the tube axis. FIG. 3 shows the formed
sample created, while FIG. 4 presents the dimensional analysis of
the cross sectional deformation at an arbitrary cross section in
the middle of the expanded section. After the forming experiment,
the length of the sample decreased to 116.59 mm. The perimeter of
the cross sectional profile increased by 14.4%, whereas the minimum
wall thickness decreased to 0.71 mm. This accounts for 20% of the
wall thinning The cross sectional area increased by 4.7%. Corner
radii of the die cavity were machined with the 2.38 mm-radius end
mill. As seen in FIG. 4, the outer radii of the expanded section
were almost precisely equal to the die cavity radii.
[0056] Another experiment employing the systems and methods
disclosed herein involved the expansion of the AMS 4943 alloy. The
same die cavity used in the previous experiment was utilized in
this experiment. The seamless sample dimensions were 12.74 (the
outer diameter) x 0.90 (the wall thickness).times.118.82 (the tube
length) mm. FIG. 5 depicts the cross sectional geometry of the
generated shape. The length of the sample after the experiment was
115.87 mm. The perimeter increased by 12.29% and minimum wall
thickness decreased to 0.76 mm (18.3% of the wall thinning) The
cross sectional area increased by 4.6%. The radii of the generated
shape were 2.86 and 3.06 mm.
[0057] The seamless tube made of the AMS 5581 alloy was the subject
of another experiment. The forming process of this embodiment was
dual-sided. The sample dimensions prior to forming were
12.75.times.0.89.times.117.98 mm. FIG. 6 is a photograph of the
formed workpiece. FIG. 7 describes the cross sectional geometry of
the formed shape. The length of the sample after the experiment was
115.57 mm. The perimeter increased by 27.1% and the minimum wall
thickness decreased to 0.69 mm (29.6% of the wall thinning) The
cross sectional area increased by 7.4%. The radii of the formed
shape were 3.05, 3.33, 3.58, and 3.66 mm.
[0058] Another experiment for yet another exemplary embodiment of
the present invention involved the two-sided expansion of the AMS
4943 alloy. The geometry of the die cavity remained the same as in
previous experimentation. The seamless sample dimensions were
12.74.times.0.90.times.117.98 mm. FIG. 8 presents the analysis of
the cross sectional geometry. The total length of the sample
decreased to 113.79 mm while the perimeter increased by 24.9%. The
wall thickness at the investigated cross section decreased to 0.77
mm which accounts for 16.7% of the wall thinning while the cross
sectional area increased by 16.2%. The radii of the generated shape
were 3.10, 3.18, 3.31, and 3.62 mm.
[0059] The microstructure of the generated sample using this
particular embodiment was investigated. The Ti-3A1-2.5V alloy is
more brittle than chromium-nickel alloys and its tensile elongation
limit is half of the elongation limit of these alloys; therefore,
the tested sample inclined toward cracking when subjected to
excessive deformations. FIG. 9 shows a polished and etched sample
cross section of the deformed sample. No indications of crack
development were observed.
[0060] The significant expansion of an AMS 4943 tube was the
subject of a further experiment in accordance with the present
disclosures. The seamless tube sample dimensions before expansion
were 12.74.times.0.90.times.117.60 mm. A die cavity was made out of
the CerroBend 158 alloy, which experienced a limited amount of
deformation during forming. In this embodiment, air was not
evacuated from the die cavity; nor had the cavity any air relief
openings. FIG. 10 depicts a general view of the formed tube while
FIG. 10A depicts the dimensions of its cross section. The total
length of the sample decreased to 111.00 mm. The expansion of the
outside diameter ranged between 19.50-20.00 mm, which relates to
the average increase by 55% of the perimeter of the sample. The
wall thickness at the investigated cross section decreased to 0.71
mm, which accounts for 20% of the wall thinning
[0061] Now referring to FIG. 11, an actual aerospace part, a heat
shield made of thin wall AMS 5581 and used in a tube assembly of an
aerospace engine, was a subject of the next experiment. The
dimensions of the tube before forming were
14.4.times.0.25.times.170 mm. Multiple elliptical cross sections
were formed from a single round tube. The maximum gain in a
perimeter after expansion was 18.5%. Limited spring back was
observed (within 0.003''). The partition line ridge on the formed
component, 0.006'' wide, was visible at the die dividing plane. In
this embodiment, the division line can be eliminated by changing
die design from a split die to a single piece die. For such an
embodiment, this can be achieved in an electro discharge machine by
employing a sinking electrode technique.
[0062] Traditional punch-and-die forming technologies cannot
achieve the tube sections expanded in the course of the foregoing
experiments embodiments of the present invention are inaccessible
to the traditional. Contrary to hydro expansion, in the compression
pulse forming utilized in the embodiments disclosed herein, the
process of forming of central tube sections does not involve any
obstacles. The limited presence of axial constraints of the work
piece in the exemplary embodiments allow dislocation of the sample
material toward an expanded section. Moreover, the compression
pulse forming described herein is a dynamic process where the
traveling wave acts only on a particular section of the work piece
and not on a whole tube. While a specific section of the tube is
subjected to the high pulse pressure, the pressures exerted on
other parts of the work piece are much lower (FIG. 2A). Thus, axial
friction forces between the die and the tube obstructing metal
redistribution are significantly reduced.
[0063] This hypothesis is validated by the experimental results
herein showing the shortening of tube length and increase of the
cross sectional area of the expanded component sections. The
percentage-wise decreases in the length during five forming
experiments were 1.7%, 2.5%, 2.1%, 3.7%, and 5.9%, while the
increase in the cross sectional areas in the first four experiments
were 4.7%, 4.6%, 7.4%, and 16.2% respectively. These results
clearly demonstrate the material dislocation toward the expanded
sections. This is a major advantage of embodiments disclosed
herein, which allow significant expansions of the middle of the
work piece without the axial feeding.
[0064] Despite significantly reduced axial friction, there is a
presence of circumferential friction. This is demonstrated by
experiments involving one-sided expansion (FIGS. 4 and 5). The
circumferential friction, between a tube and a die, acts in the
plane perpendicular to the work piece axis. This contributes to
formation of limited deformation zones (dead zones). During the
experiments, the material did not flow uniformly along the whole
work piece perimeter for certain exemplary embodiments. FIGS. 4 and
5 show no material elongation over approximately 1/3 of tube cross
sections. This indicates that friction forces overcame expansion
forces acting along the perimeter, which resulted directly in
limited material elongation in the dead zone. However, when other
embodiments utilized double sided expansion (FIGS. 7 and 8), the
presence of dead zones was significantly reduced.
[0065] The feasibility to generate complex hollow shapes is
demonstrated by the forming of the AMS 5581 and AMS 4943 alloys
(FIGS. 7 and 8). The double-sided deformation of tubes was
accomplished using dies containing cavities in both split halves.
Reduced contact areas between dies and work pieces allowed uniform
material thinning along the whole perimeter of expanded shapes. The
comparison of experiments involving expansion of the AMS 4943 alloy
shows the relation between the wall thinning and the die contact
area.
[0066] The experimental results depicted in FIGS. 5 and 8 were
compared. In one embodiment involving one-sided expansion of a
titanium alloy, the difference between the maximum and minimum wall
thicknesses was 17%, while the same ratio for an embodiment
utilizing a two-sided expansion was 6%. The attained uniform wall
thinning, with structurally sound corner radii, constitutes an
important result not attainable in quasi-static forming
processes.
[0067] The experiment to form a titanium alloy as shown in FIG. 10
demonstrates the capability of a significant expansion of
hard-to-form materials characterized by high tensile strength, low
modulus of elasticity, large spring back, and low static elongation
limits. A local 55% increase in the AMS 4943 tube diameter was
attained. The result significantly surpasses cold forming strain
limits. The increase in material ductility is comparable with hot
forming at approximately 600.degree. C.-800.degree. C. The hot
forming process is a male-female die process, which has limited
access to the middle sections of a tubular work piece. Moreover,
due to oxygen air, hot forming produces a visible surface oxide
scale and diffused-in oxygen layer (alpha case). This brittle layer
requires removal by pickling in HF-HNO3 acid solutions, otherwise a
formed product would be susceptible to fatigue cracking Due to
these shortcomings, the hot forming has the status of a special
process, which has to be regulated by third party approvals.
[0068] Despite imperfections of manually manufactured dies
resulting in visible minor deficiencies of the generated shapes,
the samples created in the experiments had considerably reduced
spring back. Examples involving both alloys (Inconel 625 and
Ti-3A1-2.5V), characterized by a significant spring back in
quasi-static forming, show a limited evidence of spring back. As
demonstrated in FIGS. 7 and 8, the height and width of expanded
shapes precisely reproduced (within 0.002'') these dimensions of
the die cavity. Moreover, a thin wall component presented in FIG.
11, in which all dimensions are in agreement within 0.003'' of the
die dimensions, confirms the feasibility of precision forming, a
major advantage over the prior art, using the apparatus and methods
disclosed herein. The compression pulse traveling at the speed of
sound is sufficient to generate strain rates adequate to overcome
the spring back.
EXAMPLE
[0069] Now referring to FIGS. 12 and 12A, a compressor high
pressure stage bleed tube for commercial applications was formed in
accordance with the present disclosures. The bleed tube was made
from OD 0.500.times.0.028 thick AMS 4943 tube.
[0070] As was shown above, multiple exemplary embodiments of the
present invention show the traveling compression waves propagate
with the speed of sound through a liquid stream flowing through a
work piece confined by a die. Due to the nature of the traveling
waves at each instant of time, only a section of a work piece and a
die are exposed to the high water pressure. Thus while super-high
pressure is exerted on the die halves, the total force separating
them is rather limited. This significantly simplifies, and in fact
makes practical, the design of tools for the implementation of the
proposed forming technology described herein.
[0071] Although the systems and methods of the present disclosure
have been described with reference to exemplary embodiments
thereof, the present disclosure is not limited thereby. Indeed, the
exemplary embodiments are implementations of the disclosed systems
and methods are provided for illustrative and non-limitative
purposes. Changes, modifications, enhancements and/or refinements
to the disclosed systems and methods may be made without departing
from the spirit or scope of the present disclosure. Accordingly,
such changes, modifications, enhancements and/or refinements are
encompassed within the scope of the present invention.
[0072] All references cited are incorporated herein by reference in
their entireties.
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* * * * *
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